Compactors are used for compacting various surfaces and materials associated with roads, landfills and construction sites. For example, road builders use compactors to compact asphalt, soil, gravel and other materials during road construction and repair. Thorough compaction of the underlying ground and each layer of a road provides the requisite structural stability for the road. Landfill operators use compactors to maximize the use of a landfill by compacting trash to create space for additional trash. Compacting the trash in a landfill also helps to increase the structural stability of the landfill.
One type of compactor is a drum-type compactor having a heavy rotating drum for compacting or crushing the material over which the compactor is driven. In addition to the drum, such compactors may include two rear wheels and a frame. The weight of the compactor may provide the necessary weight and force for compaction. Additionally, the total weight of a compactor may be controlled by adding ballast, such as steel, concrete, calcium chloride, sand and/or water.
Drum-type compactors may have a vibratory mechanism that includes movable weights arranged within the drum. Shifting the positions of the weights inside the drum induces vibrational forces that are imparted to the surface, aiding compaction. The amplitude and frequency of the vibrations may be controlled to increase the degree of compaction. Accelerometer-based measurement systems may sense the vibrational return and provide the operator with an indication of what conditions exist at or beneath the surface being compacted. Alternatively, soil conditions and stiffness can be measured using rolling resistance data from the drum and/or the wheels.
Despite the use of a compactor, soft spots may occur in a surface that is being compacted. Soft spots may create safety hazards, reduce vehicle traction or preclude a stable foundation with a known and uniform density. Such soft spots are known to occur during road construction, landfill compaction or in almost any surface that is being compacted. As soft spots may not be visible to an operator of a compactor or other member of the crew, identifying and recording the location of soft spots is necessary for their timely and fast repair. These repairs may be accomplished by various means, including adding material to the soft spot, removing the soft material and replacing it with denser material, making additional passes over the soft spot with the compactor and/or digging up a foreign object that may be buried under the surface.
However, because soft spots may not be clearly visible, precisely locating a soft spot that has been traversed by a compactor remains problematic because there is no convenient means for recording the precise location of a soft spot or transmitting the precise location of a soft spot to a repair crew. U.S. Pat. No. 8,073,609 (Koch) discloses a system for sensing slippage of a truck or vehicle travelling on a road or path and recording the location of the slippage on a map. The system of Koch uses the recorded location by adjusting a speed and/or steering angle of a truck subsequently travelling through the recorded location in response to an anticipated or actual slip.
There is a need for an improved compactor capable of more accurately identifying and recording the location of soft spots so soft spots can be quickly and properly repaired.